Atoms and Molecules

Category archives for Atoms and Molecules

Laser-Cooled Atoms: Sodium

Element: Sodium (Na) Atomic Number: 11 Mass: one stable isotope, 23 amu Laser cooling wavelength: 589 nm Doppler cooling limit: 240 μK Chemical classification: Alkali metal, column I of the periodic table. Like the majority of elements, it’s a greyish metal at room temperature. Like the other alkalis, it’s highly reactive, and bursts into flame…

Know Your Laser-Cooled Atoms

At the tail end of the cold-atom toolbox series, I joked about doing a “trading card” version shortening the posts to a more web-friendly length. In idly thinking about this, though, it occurred to me that if one were going to have cold-atom trading cards, it might make more sense to have them for the…

This is probably the last trip into the cold atom toolbox, unless I think of something else while I’m writing it. But don’t make the mistake of assuming it’s an afterthought– far from it. In some ways, today’s topic is the most important, because it covers the ways that we study the atoms once we…

Bose Condensation of Coffee?

Writing up the evaporative cooling post on cold atom techniques, I used the standard analogy that people in the field use for describing the process: cooling an atomic vapor to BEC is like the cooling of a cup of coffee, where the hottest component particles manage to escape the system of interest, and what’s left…

In our last installment of the cold-atom toolbox series, we talked about why you need magnetic traps to get to really ultra-cold samples– because the light scattering involved in laser cooling limits you to a temperature that’s too high for making Bose-Einstein condensation (BEC). This time out, we’ll talk about how you actually get to…

We’re getting toward the end of the cold-atom technologies in my original list, but that doesn’t mean we’re scraping the bottom of the barrel. On the contrary, the remaining tools are among the most important for producing and studying truly ultra-cold atoms. Wait, isn’t what we’ve been talking about cold enough? There is, as always,…

Today’s dip into the cold-atom toolbox is to explain the real workhorse of cold-atom physics, the magneto-optical trap. This is the technology that really makes laser cooling useful, by letting you collect massive numbers of atoms at very low temperatures and moderate density. Wait a minute, I thought we already had that, with optical molasses?…

This topic is an addition to the original list in the introductory post for the series, because I had thought I could deal with it in one of the other entries. Really, though, it deserves its own installment because of its important role in the history of laser cooling. Laser cooling would not be as…

Why Do Small Science?

I spent an hour or so on Skype with a former student on Tuesday, talking about how physics is done in the CMS collaboration at the Large Hadron Collider. It’s always fascinating to get a look at a completely different way of doing science– as I said when I explained my questions, the longest author…

Last time in our trip through the cold-atom toolbox, we talked about light shifts, where the interaction with a laser changes the internal energy states of an atom in a way that can produce forces on those atoms. This allows the creation of “dipole traps” where cold atoms are held in the focus of a…